The present invention relates to fixtures and a method for accurately setting probe depth and, more particularly, to a fixture and method for accurately setting dynamic pressure probe depth in a combustion liner.
As part of the monitoring controls and diagnostic tools for an operating combustion system in a rotary machine such as a gas turbine, it is necessary to measure and acquire various data including combustion chamber dynamic pressure. This data is used to confirm proper operational health of the combustion system, and is also used to tune the gas turbine engine so that it is operating with an appropriate balance between combustion dynamics and emissions.
The combustion dynamics measurement probe holder should be inserted to the combustion can so that the tip aligns itself at a certain depth relative to the combustion liner. Typically, the tip is set about 0.030xe2x80x3 back from the inside of the liner. The depth of the tip should be identical for all probes used in the turbine.
One way of achieving identical probe depth is to remove the combustion can cover and combustion hardware so that the tip of the probe can be set by measuring its position relative to the inside wall of the combustion liner. Thus, currently, after each combustion can of the turbine is disassembled, the probe depth is set visually. It would be desirable to provide for an accurate and consistent probe tip placement without requiring removal of the combustion hardware and disassembly of the combustion cans of the turbine.
The invention provides fixtures and a method for setting the depth of the combustion dynamics probe tip repeatably and accurately in all combustion cans of the turbine.
The fixture of the invention is provided in accordance with an exemplary embodiment as a kit of tools or fixtures for measuring and transferring probe depth. A first, measuring fixture of the kit measures the depth to which the tip of the probe should be set. The acquired depth is then applied to the probe(s) for installation. In an exemplary embodiment, the measurement acquired by the measurement fixture is transferred to a second device that can apply the measured depth to the probe itself. This process ensures that the probe will be placed in a proper position to accurately measure, e.g., the dynamic pressure of the combustion process and eliminate any inconsistencies in measurement that would result from having the probe tips inserted at different depths.
Thus, the invention is embodied in a kit for setting probe depth, comprising a measurement fixture for measuring a target probe insertion depth through a wall of a component, said measurement fixture including a shaft and a tip portion provided at a distal end of said shaft, and an indicator for indicating said target depth on said shaft; and a transfer fixture for transferring a depth indicated by said indicator of said measurement fixture to a probe holder device. The transfer fixture including a housing defining a receptacle for receiving said shaft and said tip portion, the receptacle having an adjustable depth to selectively correspond to the depth indicated by the indicator of the measurement fixture, whereby a probe holder device may thereafter be disposed in said transfer fixture to a depth corresponding to said indicated depth and marked.
The invention is also embodied in a method of accurately placing a probe to a target depth comprising: providing an assembly for receiving the probe comprising a first, liner wall and a second, casing wall, a receptacle being defined in the first wall for receiving a tip of the probe; providing a measurement fixture having a shaft and a tip portion projecting from said shaft a distance corresponding in length to a target length of the probe inwardly from an outer surface of said first, liner wall; disposing the measurement fixture through an orifice defined in said second, casing wall and inserting said tip portion into said receptacle to abut said shaft of said measurement fixture against said outer surface of said liner wall; providing an indication of a position of said shaft at a predetermined point with respect to said second, casing wall; providing a transfer fixture including a housing having a receptacle of variable depth for receiving the measurement fixture; inserting said shaft into said receptacle so that said position indicator is aligned with a predetermined, complimentary portion of the fixture; adjusting a depth of said receptacle so that a bottom of the receptacle engages the tip portion; removing the measurement fixture; inserting a probe holder device into said receptacle so that the probe tip engages the bottom of the receptacle; and marking said probe at a point corresponding to said complimentary portion.